Chaos Monkeyware works on a smaller scale. It is a Express/Connect
compatible middleware for Node.js web applications that causes random
failures. The failure propability is configurable (default is 10%).

The currently included failure modes (called mischiefs) are:

Crash – exits the Node.js process before it has a chance to respond to
the HTTP request. I hope you have a process monitor…

Delay – provides the normal HTTP response, but with an added (random)
delay of 1-10 seconds.

HTTP 403 Access Denied

HTTP 404 Not Found

HTTP 500 Internal Server Error

Currently, all of these mischiefs have equal propability. Future
releases might support adjusting their probability individually or even
disabling some of them individually.